This invention relates generally to improved means and methods for providing very fast binary coded decimal (BCD) to binary conversion, and more particularly to providing such BCD-to-binary conversion in connection with the addressing of a digital memory.
Recent advances in integrated circuit technology have made possible significant increases in the speed of operation of digital computers. As a result, there has been increased emphasis on developing very fast BCD-to-binary converters which will not deleteriously affect the speed of data processing operations.
Various known approaches for providing BCD-to-binary conversion are disclosed in the articles: "A Method for High Speed BCD-to-Binary Conversion", L. C. Beougher, Computer Design, March 1973, pp. 53-59; "Binary-to-Decimal Conversion with Complex IC Functions", J. R. Linford, Computer Design, September 1970, pp. 53-61; and "Storage Efficient Representation of Decimal Data", Tien Chi Chen, Communications of the ACM, January 1975, Vol. 18, No. 1, pp. 49-52.
BCD-to-binary approaches specifically directed to providing BCD-to-binary conversion in connection with the addressing of a memory are, for example, disclosed in U.S. Pat. Nos. 3,160,872 and 3,618,047; in the article E. J. Lengyel et al., "Direct Decimal to Binary Address Generator for Small Memories", IBM Technical Disclosure Bulletin, Vol. 9, No. 10, March 1967; and also in the commonly assigned copending patent application Ser. No. 118,490, filed Feb. 4, 1980 for "Circuit for Addressing Binarily Addressable Memories with BCD Addresses", H. Potash, inventor, now U.S. Pat. No. 4,334,213.
BCD-to-binary converters, such as disclosed above, are not fast enough to meet the high speed requirements of many current high speed computers now under development so that a need exists for faster BCD-to-binary converters. This is a particular problem with regard to memory addressing, since the time required for conversion directly impacts on the memory access time. Accordingly, it is a primary object of the present invention to provide a relatively simple, very fast BCD-to-binary converter which is particularly useful for addressing a digital memory.